The present invention relates to loose-fill or blowing wool insulation for sidewall or attic installation, and more particularly to a blended loose-fill insulation which utilizes irregularly-shaped glass fibers and provides improved coverage and reduced convection.
The use of glass fiber blowing wool or loose-fill insulation is well-known and increasing in popularity. Loose-fill insulation is preferred by many contractors because it can be easily and quickly applied in both new construction as well as in existing structures. Further, loose-fill insulation is a relatively low cost material.
As the name implies, loose-fill insulation is not Breed into a blanket or batt prior to installation. Rather, the product is generally installed by pneumatically blowing the loose-fill insulation into the desired area. Accordingly, loose-fill fiberglass insulation in an unconstrained space, such as an attic, is not as compacted as blanket insulation, occupying a greater volume than an equivalent amount of blanket insulation. As a result, the thermal conductivity or k value of loose-fill insulation in current use is generally higher than that of blanket insulation. That is, loose-fill insulation currently used in the industry does not inhibit the conduction of heat as well as blanket insulation. To compensate for the higher conductivity of loose-fill, it is applied in greater depth than blanket insulation to achieve an equivalent R-value.
Furthermore, in many applications, increased insulation depth is either not possible or impractical. For example, in sidewall installation, the depth (or in this instance the thickness of the wall) is limited by standard wall thicknesses such as 3.5 inches (8.9 cm) for a 2.times.4 (5.times.10 cm) wall or 5.5 inches (14 cm) for a 2.times.6 (5.times.15.2 cm) wall. To compensate for such thickness limits, a higher density loose-fill must be employed. In other words, more glass must be blown into the same mount of space. Also, in practice it has remained quite difficult to uniformly blow the required higher densities into the confined spaces of sidewalls.
When designing loose-fill or blown insulation products of glass fibers, the ideal insulation would have uniform spacing and density once installed. That is, the final product would preferably be free of gaps, spaces or voids between fibers. Insulation is basically a lattice for trapping air between the fibers and thus preventing movement of air. The lattice also retards heat transfer by scattering radiation. A more uniform spacing and density of the insulation would minimize air movement under extreme cold conditions and maximize scattering and, therefore, would have greater insulating capability.
Traditional loose-fill or blown insulation comprises traditional, straight, short fibers. Baits of traditional bindered or unbindered glass fibers are cut, milled, or otherwise formed into nodules, and then compressed and bagged for shipment. Upon installation, the compressed loose-fill is added to the hopper of a blowing machine where the loose-fill is mechanically opened and broken into smaller portions. However, after being blown into position, numerous small gaps or voids remain between the blown portions of insulation. These voids raise the thermal conductivity of the insulation, requiring more glass to be employed to achieve a specified insulating value.
While lighter density loose-fill insulating materials have been developed, a problem with convection within the body of the material occurs under extreme cold temperatures which adversely affects the R-value. For example, primarily straight bindered fibers of loose-fill insulation may be comprised of 1/2" milled nodules which are relatively large and very low in density. As a result, when the nodules are spread out or blown into place, there are voids in the interstices between the nodules which allow some convection of cold air.
Accordingly, a need exists for an improved loose-fill insulating material with a uniform volume filling nature and to an insulating material which provides good coverage and thermal efficiency when blown.